U.S. patent application number 14/142912 was filed with the patent office on 2014-07-03 for fan control circuit.
This patent application is currently assigned to Hon Hai Precision Industry Co., Ltd. The applicant listed for this patent is Hon Hai Precision Industry Co., Ltd., Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd.. Invention is credited to HAI-QING ZHOU.
Application Number | 20140184126 14/142912 |
Document ID | / |
Family ID | 50991081 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140184126 |
Kind Code |
A1 |
ZHOU; HAI-QING |
July 3, 2014 |
FAN CONTROL CIRCUIT
Abstract
A fan control circuit includes a hardware controller, a
rectifier circuit, first to third electronic switches, and a fan.
When the hardware controller outputs a pulse width modulation (PWM)
signal to the rectifier circuit and the fan, the rectifier circuit
transforms the PWM signal into a direct current (DC) voltage and
outputs the DC voltage to the first electronic switch. The first
electronic switch is turned on, and the second and third electronic
switches are turned off. A rotation speed of the fan is controlled
by the PWM signal received from the hardware controller. When the
hardware controller does not output the PWM signal, the first
electronic switch is turned off, the second and third electronic
switches are turned on, a DC power supply supplies power to the fan
through the third electronic switch, and the fan rotates at full
speed.
Inventors: |
ZHOU; HAI-QING; (Shenzhen,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hon Hai Precision Industry Co., Ltd.
Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. |
New Taipei
Shenzhen |
|
TW
CN |
|
|
Assignee: |
Hon Hai Precision Industry Co.,
Ltd
New Taipei
TW
Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd
Shenzhen
CN
|
Family ID: |
50991081 |
Appl. No.: |
14/142912 |
Filed: |
December 29, 2013 |
Current U.S.
Class: |
318/503 |
Current CPC
Class: |
H02P 7/29 20130101; H02P
7/00 20130101 |
Class at
Publication: |
318/503 |
International
Class: |
H02P 7/00 20060101
H02P007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2012 |
CN |
2012105828122 |
Claims
1. A fan control circuit comprising: a first resistor and a second
resistor; a fan comprising a control pin; a hardware controller
connected to the control pin of the fan; a rectifier circuit
connected to the hardware controller; a first electronic switch
comprising a first terminal connected to the rectifier circuit, a
second terminal connected to a direct current (DC) power supply
through the first resistor, and a third terminal grounded; a second
electronic switch comprising a first terminal connected to the
second terminal of the first electronic switch, a second terminal
connected to the DC power supply through the second resistor, and a
third terminal grounded; and a third electronic switch comprising a
first terminal connected to the second terminal of the second
electronic switch, a second terminal connected to the control pin
of the fan, and a third terminal connected to the DC power supply;
wherein when the hardware controller outputs a pulse width
modulation (PWM) signal to the rectifier circuit and the control
pin of the fan, the rectifier circuit transforms the PWM signal
into a DC voltage and outputs the DC voltage to the first
electronic switch, the first electronic switch is turned on, the
second and third electronic switches are turned off, a rotation
speed of the fan is controlled by the PWM signal received from the
hardware controller; and wherein when the hardware controller does
not output the PWM signal, the rectifier circuit does not output
the DC voltage, the first electronic switch is turned off, the
second and third electronic switches are turned on, the DC power
supply supplies power to the control pin of the fan through the
third electronic switch, and the fan rotates at full speed.
2. The fan control circuit of claim 1, wherein the rectifier
circuit comprises a diode, a capacitor and a third resistor, the
diode comprises an anode connected to the hardware controller, and
a cathode grounded through the third resistor and the capacitor in
that order.
3. The fan control circuit of claim 2, further comprising a fourth
resistor, wherein the first terminal of the first electronic switch
is connected to a node between the third resistor and the
capacitor, and is grounded through the fourth resistor.
4. The fan control circuit of claim 3, wherein the first electronic
switch is an npn-type bipolar junction transistor (BJT), and the
first terminal, the second terminal, and the third terminal of the
first electronic switch respectively a base, a collector, and an
emitter of the npn-type BJT.
5. The fan control circuit of claim 1, further comprising a light
emitting diode (LED) comprising an anode connected to the DC power
supply through the second resistor, and a cathode connected to the
second terminal of the second electronic switch, wherein when the
second electronic switch is turned on, the LED is lit up.
6. The fan control circuit of claim 5, further comprising a fifth
resistor, wherein the first terminal of the third electronic switch
is connected to the second terminal of the second electronic switch
through the fifth resistor.
7. The fan control circuit of claim 6, wherein the second
electronic switch is an npn-type BJT, and the first terminal, the
second terminal, and the third terminal of the first electronic
switch respectively a base, a collector, and an emitter of the
npn-type BJT.
8. The fan control circuit of claim 6, wherein the third electronic
switch is a pnp-type BJT, and the first terminal, the second
terminal, and the third terminal of the third electronic switch
respectively a base, a collector, and an emitter of the pnp-type
BJT.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present disclosure relates to control circuits, and
particularly to a fan control circuit.
[0003] 2. Description of Related Art
[0004] In most computer systems, hardware controllers function as
temperature monitoring elements, to transmit pulse width modulation
(PWM) signals to adjust a rotation speed of fans, according to a
temperature of the computer systems. However, if the hardware
controllers operate abnormally and fail to transmit the PWM
signals, the fans will stop running. Therefore, heat cannot be
dissipated timely, which may affect normal operation of the
computer systems and damage the computer systems.
BRIEF DESCRIPTION OF THE DRAWING
[0005] Many aspects of the present disclosure can be better
understood with reference to the following drawings. The components
in the drawings are not necessarily drawn to scale, the emphasis
instead being placed upon clearly illustrating the principles of
the present embodiments. Moreover, in the drawings, like reference
numerals designate corresponding parts throughout the views.
[0006] The figure is a circuit diagram of an embodiment of a fan
control circuit.
DETAILED DESCRIPTION
[0007] The disclosure, including the accompanying drawings, is
illustrated by way of examples and not by way of limitation. It
should be noted that references to "an" or "one" embodiment in this
disclosure are not necessarily to the same embodiment, and such
references can mean "at least one."
[0008] The figure shows an embodiment of a fan control circuit 100
for controlling a rotation speed of a fan 80. In one embodiment,
the fan control circuit 100 includes a temperature sensor 10, a
central processing unit (CPU) 20, a platform controller hub (PCH)
30, a hardware controller 50, a rectifier circuit 60, three
electronic switches Q1-Q3, four resistors R2-R5, and a light
emitting diode (LED) D2. The rectifier circuit 60 includes a diode
D1, a resistor R1, and a capacitor C1. The fan 80 includes a power
pin VCC, a control pin PWM, a detecting pin TACH, and a ground pin
GND. Each of the electronic switches Q1-Q3 includes a first
terminal, a second terminal, and a third terminal In one
embodiment, the fan control circuit 100 is used in a computer
system.
[0009] The CPU 20 is electrically connected to the temperature
sensor 10 and the PCH 30. The hardware controller 50 is
electrically connected to the PCH 30, an anode of the diode D1, the
control pin PWM of the fan 80, and the detecting pin TACH of the
fan 80. A cathode of the diode D1 is grounded through the resistor
R1 and the capacitor C1 in that order. The first terminal of the
electronic switch Q1 is electrically connected to a node between
the resistor R1 and the capacitor C1, and grounded through the
resistor R2. The second terminal of the electronic switch Q1 is
electrically connected to a direct current (DC) power supply Vcc
through the resistor R3. The third terminal of the electronic
switch Q1 is grounded. The first terminal of the electronic switch
Q2 is electrically connected to the second terminal of the
electronic switch Q1. The second terminal of the electronic switch
Q2 is electrically connected to a cathode of the LED D2. The third
terminal of the electronic switch Q2 is grounded. An anode of the
LED D2 is electrically connected to the DC power supply Vcc through
the resistor R4. The first terminal of the electronic switch Q3 is
electrically connected to the second terminal of the electronic
switch Q2 through the resistor R5. The second terminal of the
electronic switch Q3 is electrically connected to the control pin
PWM of the fan 80. The third terminal of the electronic switch Q3
is electrically connected to the DC power supply Vcc. The power pin
VCC of the fan 80 is electrically connected to a DC power supply
12V. The ground pin of the fan is grounded.
[0010] In use, the temperature sensor 10 senses a temperature of
the computer system, and outputs the sensed temperature to the CPU
20. The CPU 20 outputs a control signal to the hardware controller
50 through the PCH 30 according to the sensed temperature received
from the temperature sensor 10. If the hardware controller 50
operates normally, the hardware controller 50 outputs a pulse width
modulation (PWM) signal having a duty cycle corresponding to the
control signal to the rectifier circuit 60 and the control pin PWM
of the fan 80. The rectifier circuit 60 transforms the PWM signal
into a DC voltage, and outputs the DC voltage to the first terminal
of the electronic switch Q1. The electronic switch Q1 is turned on
after receiving the DC voltage output by the rectifier circuit 60,
and the electronic switches Q2 and Q3 are turned off. Thus, the LED
D2 is not lit up, which indicates that the hardware controller 50
operates normally. The rotation speed of the fan 80 is controlled
by the PWM signal received from the hardware controller 50.
[0011] If the hardware controller 50 does not operate normally and
does not output the PWM signal, the rectifier circuit 60 does not
output the DC voltage. Thus, the electronic switch Q1 stays turned
off, and the electronic switches Q2 and Q3 are turned on. When the
electronic switches Q2 and Q3 are turned on, the LED D2 is lit up
to indicate that the hardware controller 50 does not output the PWM
signal and should be repaired or replaced. Furthermore, when the
switches Q2 and Q3 are turned on, the DC power supply Vcc supplies
power to the control pin PWM of the fan 80 through the electronic
switch Q3, so that the fan 80 rotates at full speed. Therefore,
even if the hardware controller 50 does not output the PWM signal,
the fan 80 continues to operate to dissipate heat from the computer
system.
[0012] In one embodiment, each of the electronic switches Q1 and Q2
is an npn-type bipolar junction transistor (BJT), and the
electronic switch Q3 is a pnp-type BJT. The first terminal, the
second terminal, and the third terminal of each of the electronic
switches Q1 and Q2 are a base, a collector, and an emitter of the
npn-type BJT, respectively. The first terminal, the second
terminal, and the third terminal of the electronic switch Q3 are a
base, a collector, and an emitter of the pnp-type BJT,
respectively. In other embodiments, each of the electronic switches
Q1 and Q2 can be an n-channel metal-oxide semiconductor
field-effect transistor or another type of electronic switch having
similar functions. The electronic switch Q3 can be a p-channel
metal-oxide semiconductor field-effect transistor or another type
of electronic switch having similar functions. The LED D2 can be
replaced by a buzzer or another type of indicator having similar
functions. The LED D2 can be omitted if power consumption and
operation states of the hardware controller 50 are not essential to
regulate.
[0013] Even though numerous characteristics and advantages of the
disclosure have been set forth in the foregoing description,
together with details of the structure and function of the
disclosure, the disclosure is illustrative only, and changes may be
made in detail, especially in the matters of shape, size, and
arrangement of parts within the principles of the disclosure to the
full extent indicated by the broad general meaning of the terms in
which the appended claims are expressed.
* * * * *